This unusual circumstance means that tracking the path of water, both above the ground and below the surface, is an urgent task. Gutter to Gulf has developed a taxonomy to describe and explain surface and subsurface drainage patterns and mechanisms.

The need to pump water out of New Orleans is the direct consequence of land use strategies that drained the city's back-of-town swamps. Over the last century, the city has taken on the shape of a bowl: its bottom is below sea level and its sides are formed by high levees. The high water table typical of deltas means that rainwater cannot infiltrate the soil. On the contrary, groundwater is constantly expressed at the surface and must be pumped out to Lake Pontchartrain along with rainwater.

Hidden behind high levee walls or underground, the infrastructure that carries water out of New Orleans is hard to see. Its invisibility is dangerous: this essential system is hard to see, hard to understand, and easy to forget.